1. Field of the Invention
The present invention relates to a recording thin film magnetic head used with, for example, a flying magnetic head and, more particularly, to a thin film magnetic head adapted to reduce inductance and capable of handling higher recording frequencies, and a manufacturing method for the same.
2. Description of the Related Art
FIG. 27 is a partial front view showing a construction of a conventional thin film magnetic head or inductive head, and FIG. 28 is a partial sectional view of the thin film magnetic head cut along the line XXVIIIxe2x80x94XXVIII shown in FIG. 27 and viewed from the direction of an arrow.
Reference numeral 1 shown in FIGS. 27 and 28 denotes a lower core layer formed of a magnetic material, such as Permalloy. An insulating layer 9 is deposited on the lower core layer 1.
The insulating layer 9 includes a groove 9a having an inner width represented by a track width Tw, the groove 9a extending in a height direction or Y direction in the drawing, from a surface facing a recording medium (hereinafter referred to as xe2x80x9cABSxe2x80x9d which stands for air bearing surface).
In the groove 9a, a lower magnetic pole layer 3 magnetically connected to the lower core layer 1, a gap layer 46, and an upper magnetic pole layer 5 magnetically connected to an upper core layer 48 are deposited by sequentially plating in this order from bottom.
Referring to FIG. 28, a spirally formed coil layer 7 is provided on the insulating layer 9 in a portion in the height direction or the Y direction in the drawing from the groove 9a formed in the insulating layer 9.
The coil layer 7 is covered by a coil insulating layer 47 formed of a resist or the like, and an upper core layer 48 is deposited on the coil insulating layer 47. The upper core layer 48 is magnetically connected with the upper magnetic pole layer 5 at a distal end portion 48a and also magnetically connected to the lower core layer 1 at a proximal end portion 48b. 
In the inductive head shown in FIGS. 27 and 28, when recording current is supplied to the coil layer 7, a recording field is induced in the lower core layer 1 and the upper core layer 48. Magnetic signals are recorded in a recording medium, such as a hard disc, by a leakage field from between the lower magnetic pole layer 3 magnetically connected to the lower core layer 1 and the upper magnetic pole layer 5 magnetically connected to the upper core layer 48.
In the inductive head shown in FIGS. 27 and 28, a lower magnetic pole layer 3 locally formed over the track width Tw, the gap layer 46, and the upper magnetic pole layer 5 are provided in the vicinity of the surface facing the recording medium. This type of inductive head permits a narrower track.
The following will describe a manufacturing method for the inductive head shown in FIGS. 27 and 28. First, the insulating layer 9 is deposited on the lower core layer 1, then the groove 9a having the track width Tw is formed in the insulating layer 9 for a predetermined length in the height direction (depth direction) from the surface facing the recording medium (air bearing surface).
In the groove 9a, the lower magnetic pole layer 3, the gap layer 46, and the upper magnetic pole layer 5 are continuously plated, then the coil layer 7 is pattern-deposited on a portion of the insulating layer 9 that is located behind (in the height direction) from the groove 9a formed in the insulating layer 9.
The coil layer 7 is covered by a coil insulating layer 47, and the upper core layer 48 is formed from the top of the upper magnetic pole layer 5 to cover the coil insulating layer 47 by the flame plating process. This completes the inductive head shown in FIGS. 27 and 28.
For a trend toward higher recording densities and higher recording frequencies, it is necessary to reduce a track width and the inductance of an inductive head.
In order to reduce inductance, a magnetic path formed via the upper core layer 48 from the lower core layer 1 must be made shorter. This requires that a width T1 of the coil layer 7 formed from the distal end portion 48a to the proximal end portion 48b of the upper core layer 48 be reduced. Reducing the width T1 of the coil layer 7 allows the upper core layer 48 to be shortened so as to achieve a shorter magnetic path.
A method for forming the coil layer 7 by two layers could be applied to decrease the width T1 of the coil layer 7 without changing the number of turns of the coil layer 7.
In the construction of the thin film magnetic head shown in FIGS. 27 and 28, however, the magnetic path cannot be made sufficiently shorter to be able to handle higher recording frequencies in the future merely by providing the coil layer 7 with the double-layer construction. This makes it difficult to achieve an appropriate reduction in inductance.
A reason for the difficulty mentioned above is that the coil layer 7 is deposited on the insulating layer 9 having a thick film. Referring to FIG. 27, the insulating layer 9 has a film thickness H5, and the film thickness H5 is larger than or substantially identical to a total film thickness H6 of the lower magnetic pole layer 3, the gap layer 46, and the upper magnetic pole layer 5. Therefore, as shown in FIG. 28, when a junction surface between the upper magnetic pole layer 5 and the upper core layer 48 is defined as a reference plane, the coil layer 7 deposited on the insulating layer 9 is positioned more closely to the upper core layer 48 than the reference plane.
Hence, adopting the double-layer construction directly to the coil layer 7 would lead to an extremely large height from the upper surface of the lower core layer 1 to the upper surface of the coil insulating layer 47 covering the coil layer 7 even though the width T1 of the coil layer 7 can be reduced. As a result, the magnetic path cannot be shortened much, making it impossible to accomplish an appropriate reduction in inductance.
If the double-layer construction is simply applied to the coil layer 7 in the inductive head having the construction illustrated in FIG. 28, then a thickness H1 of the coil insulating layer 47 covering the coil layer 7 increases, resulting in an extremely large bulge of the coil insulating layer 47 when the upper surface of the upper magnetic pole layer 5 is defined as the reference plane.
Accordingly, it becomes difficult to pattern-form the upper core layer 48 from above the upper magnetic pole layer 5 to cover the coil insulating layer 47 by the flame plating process, posing a problem in that a portion in the vicinity of the distal end portion 48a of the upper core layer 48 cannot be formed into a predetermined shape.
If the width T2 of each conductor of the coil layer 7 is decreased, and a height H2 of each conductor is increased, then there should be no change in the volume of the coil layer, thus avoiding an increase in a coil resistance value. Furthermore, in this case, since the width T2 of each conductor can be reduced, the width T1 of the entire coil layer 7 can be reduced, permitting a further reduction in inductance by making a magnetic path even shorter.
On the other hand, however, another problem arises in that the increased height H2 of each conductor inevitably leads to an even larger bulge of the coil insulating layer 47 covering the coil layer 7, preventing the upper core layer 48 from being formed with high accuracy.
The present invention has been made with a view toward solving the problems, and it is an object of the present invention to provide a thin film magnetic head that permits a narrower track and reduced inductance by making a magnetic path shorter, and a manufacturing method for the same.
According to one aspect of the present invention, there is provided a thin film magnetic head comprising: a lower core layer; an upper core layer; and a recording portion that has magnetic pole layers and a gap layer positioned between the lower core layer and the upper core layer at a surface facing a recording medium, wherein a coil insulating layer is deposited on the lower core layer and at the rear of the recording portion in a height direction; a coil forming groove is formed in the coil insulating layer; and a coil layer for inducing a recording magnetic field to the lower core layer, the upper core layer, and the recording portion is embedded in the coil forming groove.
An object of the present invention is to realize a shorter magnetic path thereby to reduce inductance by forming a coil layer in a different position from a prior art so as to fabricate a thin film magnetic head capable of achieving a higher recording density and a higher recording frequency.
As described above, according to the present invention, the coil insulating layer is deposited on the lower core layer and at the rear in the height direction, the coil forming groove is formed in the coil insulating layer, and the coil layer is embedded in the coil forming groove.
More specifically, according to the present invention, the coil layer is formed at a position closer to the lower core layer as compared with the coil layer of the thin film magnetic head shown in FIG. 28. Hence, the present invention makes it possible to reduce the height from the top of the recording portion to the top of the insulating layer that covers the coil layer, as compared with the height in the thin film magnetic head shown in FIG. 28. Thus, the length of the upper core layer can be made smaller, allowing a more appropriate reduction in a magnetic path, with a consequent reduction in inductance.
According to the present invention, the coil forming groove is formed beforehand in the coil insulating layer deposited on the upper surface of the lower core layer, and the coil layer is embedded in the coil forming groove. This forming method is different from that for a coil insulating layer or a lower coil insulating layer disclosed in, for example, U.S application Ser. No. 09/632,450.
To be more specific, according to the method disclosed in U.S application Ser. No. 09/632,450, the coil layer is formed by the flame plating process, and the coil insulating layer is embedded in gaps between individual conductors of the coil layer. In this type of construction, the gaps are not completely filled with the coil insulating layer, leaving a danger of cavities being formed in the gaps.
Such cavities are apt to be produced because the coil insulating layer is isotropically formed by sputtering in extremely narrow coil gaps. If the cavities are formed, then a gas accumulating in the cavities expands due to heat generated when a magnetic head is driven, leading to a danger of causing a film in a thin film magnetic head to be deformed.
According to the present invention, the coil insulating layer is deposited on the entire surface of the lower core layer, the coil forming groove is formed in the coil insulating layer by, for example, a reactive ion etching process, and the coil layer is embedded in the coil forming groove.
Thus, in the invention, the coil insulating layer is not embedded in the extremely narrow gaps of the coil layer, eliminating the possibility of the problem in that cavities are produced in the coil insulating layer. Conversely, the coil layer is embedded in the coil forming groove according to the invention. Hence, although there is a danger of cavities being formed in the coil layer, the aforesaid problem can be solved by, for example, depositing the coil layer by electroplating or the like.
In a preferred form of the present invention, the upper surface of the coil insulating layer and the upper surface of the coil layer are flush with each other. In this case, it is preferable that the upper surface of the coil insulating layer and the upper surface of the coil layer have been etched using, for example, the CMP process.
In a preferred form of the present invention, when a junction surface between the recording portion and the upper core layer is defined as a reference plane, the upper surface of the coil insulating layer and the upper surface of the coil layer are flush with the reference plane.
Forming the coil layer such that its upper surface is flush with the reference plane makes it possible to maximize a thickness of the coil layer in a stepped portion between the lower core layer and the recording portion. Hence, decreasing the width of each conductor portion of the coil layer does not result in an increase in the coil resistance value that is inversely proportional to a sectional area. With this arrangement, the width of the entire coil layer ranging from the distal end portion to the proximal end portion of the upper core layer can be reduced, so that the magnetic path can be further shortened, permitting reduced inductance to be achieved.
In another preferred form of the invention, the coil insulating layer is an inorganic insulating layer formed of an inorganic material.
In yet another preferred form of the invention, an insulating under-layer is formed between the coil layer and the lower core layer. The insulating under-layer is deposited to provide appropriate magnetic insulation between the coil layer and the lower core layer. In the present invention, the insulating under-layer also serves as a stopper layer for preventing over-etching when the coil forming groove is formed in the coil insulating layer.
In a further preferred form of the invention, an insulating layer is deposited on the coil layer, and a second coil layer is deposited on the insulating layer. The second coil layer is electrically connected with the coil layer and induces a recording magnetic filed to the lower core layer, the upper core layer, and the recording portion. With this arrangement, the width of the coil layer can be further reduced and the magnetic path can be made even shorter with a consequent reduction in inductance.
In a further preferred form of the invention, the recording portion is constituted by a lower magnetic pole layer directly connected to the lower core layer, and a gap layer deposited on the lower magnetic pole layer, or constituted by an upper magnetic pole layer that is deposited on the lower core layer and directly connected with the upper core layer via a gap layer, or constituted by the lower magnetic pole layer directly connected with the lower core layer and an upper magnetic pole layer that is deposited on the lower magnetic pole layer via the gap layer and directly connected with the upper core layer. This arrangement makes it possible to fabricate a thin film magnetic head capable of achieving narrower gaps.
In another preferred form of the invention, the gap layer is composed of a nonmagnetic metal material that permits plating. Preferably, for the nonmagnetic metal material, one material or two or more different materials are selected from among NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
According to the invention, the recording portion may be constituted by a gap layer deposited on the lower core layer and an upper magnetic pole layer deposited on the gap layer, or the lower core layer may be provided with a protuberance jutting out toward an upper core layer integrally formed with the lower core layer, and the recording portion may be constituted by a gap layer deposited on the protuberance and the upper magnetic pole layer deposited on the gap layer.
In this case, the gap layer is preferably composed of an inorganic insulating material. As the inorganic insulating material, one material or two or more different materials are preferably selected from among Al2O3, SiO2, SiON, AlN, and AlSiN.
According to another aspect of the present invention, there is provided a manufacturing method for a thin film magnetic head, comprising:
(a) a step for depositing a recording portion composed of a magnetic pole layer and a gap layer on a lower core layer;
(b) a step for depositing a coil insulating layer on a lower core layer at the rear of the recording portion in a height direction;
(c) a step for depositing a resist layer on the coil insulating layer and forming a coil pattern on the resist layer by exposure;
(d) a step for etching the coil insulating layer exposed through the coil pattern of the resist layer to an extent, where a surface of the lower core layer is not reached, so as to form a coil forming groove in the coil insulating layer;
(e) a step for removing the resist layer;
(f) a step for embedding a conductive material in the coil forming groove formed in the coil insulating layer in step (d), thereby to deposit a coil layer in the coil forming groove;
(g) a step for etching the coil layer and the coil insulating layer such that, when an upper surface of the recording portion is defined as a reference plane, an upper surface of the coil insulating layer and an upper surface of the coil layer are flush with the reference plane; and
(h) a step for depositing an insulating layer on the coil layer and the coil insulating layer, then forming an upper core layer extending from the top of the insulating layer to the upper surface of the recording portion.
Thus, according to the present invention, after the recording portion is deposited on the lower core layer, the coil insulating layer is deposited over the entire surface of the lower core layer at the rear of the recording portion in the height direction.
Then, the resist layer having the coil pattern formed thereon is deposited on the coil insulating layer, the coil insulating layer exposed through the coil pattern formed in the resist layer is etched thereby to form a coil forming groove, which has substantially the same configuration as the coil pattern formed on the resist layer, in the coil insulating layer, then the coil layer is embedded in the coil forming groove.
According to the manufacturing method of the present invention, the coil layer can be formed in a step formed between the recording portion and the lower core layer. With this arrangement, the bulge of the insulating layer covering the coil layer that protrudes from the recording portion can be made smaller. As a result, a magnetic path can be made shorter and inductance can be reduced.
In the manufacturing method in accordance with the present invention, the coil insulating layer is first deposited on the lower core layer, then the coil forming groove is formed in the coil insulating layer. This arrangement prevents a problem in that a cavity is produced in the coil insulating layer, and also eliminates a danger in that a film in the thin film magnetic head is deformed due to heat generated when the magnetic head is driven.
Furthermore, according to the present invention, when the upper surface of the recording portion is defined as a reference plane, the coil layer and the coil insulating layer are etched in the step (g) so that the upper surface of the coil insulating layer and the upper surface of the coil layer are flush with the reference plane. Therefore, according to the present invention, the film thickness of the coil layer can be maximized in the stepped portion between the lower core layer and the recording portion. When the film thickness of the coil layer can be increased as mentioned above, reducing the width of each conductor portion of the coil layer does not cause the coil resistance value to increase. Hence, the width of the coil layer can be reduced to achieve an even shorter magnetic path.
In the present invention, the following step may be added between the step (b) and the step (c):
(i) a step for etching the coil insulating layer until its upper surface becomes flush with the upper surface of the recording portion.
In this step, the upper surface of the coil insulating layer can be formed into a flat surface since the surface of the coil insulating layer has been etched until the surface becomes flush with the upper surface of the recording portion after the coil insulating layer was deposited on the lower core layer. This provides an advantage in that the application of the resist layer and exposure of the resist layer in the subsequent step (c) can be performed with high accuracy.
In the present invention, the steps (a) and (b) may be replaced by the following steps:
(j) a step for depositing the coil insulating layer on the lower core layer;
(k) a step for forming a groove in the coil insulating layer in the height direction from a surface facing a recording medium; and
(l) a step for forming the recording portion composed of a magnetic pole layer and a gap layer in the groove.
From the step (j) to the step (l), the coil insulating layer is first deposited on the lower core layer, then the groove is formed in the coil insulating layer. In the groove, the recording portion is formed. In other words, the coil insulating layer and the recording portion are formed in a reverse order from the steps (a) and (b).
In a preferred form of the present invention, in the step (a) or (l), the recording portion is formed by the lower magnetic pole layer and the gap layer, or the gap layer and the upper magnetic pole layer, or the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer.
In this case, for the gap layer, it is preferable to select a nonmagnetic metal material that permits plating together with the magnetic pole layers. Preferably, for the nonmagnetic metal material, one material or two or more different materials are selected from among NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
Alternatively, according to the present invention, in the step (a), the recording portion may be formed by the gap layer and the upper magnetic pole layer, or both side surfaces of the recording portion and the surface of the lower core layer may be etched to form a protuberance, which projects toward the recording portion from the top of the lower core layer and continues from the recording portion, so that the protuberance is made integral with the lower core layer after the recording portion is formed.
In this case, the gap layer is preferably composed of an inorganic insulating material. As the inorganic insulating material, one material or two or more different materials are preferably selected from among Al2O3, SiO2, SiON, AlN, and AlSiN.
In another preferred form of the present invention, to deposit the coil insulating layer on the lower core layer, an insulating under-layer is deposited on the lower core layer beforehand, and the coil forming groove is concavely formed in the coil insulating layer in the step (d) within a limit so that the surface of the insulating under-layer is not exposed.
The insulating under-layer serves as a xe2x80x9cstopper layerxe2x80x9d for preventing over-etching of the coil insulating layer in the step (d). Etching the coil insulating layer with the limit so that the surface of the insulating under-layer is not exposed ensures that at least the insulating under-layer lies between the lower core layer and the coil layer. This arrangement allows proper magnetic insulation to be provided between the lower core layer and the coil layer.
In the present invention, the coil insulating layer is preferably formed by an inorganic insulating material. This allows the surface of the coil insulating layer to be easily and properly etched in the step (g) or (i).
In a further preferred form of the present invention, in the step (h), after the insulating layer is deposited on the coil layer and the coil insulating layer, a second coil layer to be electrically connected to the coil layer is deposited on the insulating layer, then the upper core layer is formed on the second coil layer via the insulating layer. With this arrangement, the width of the coil layer can be further reduced, and inductance can be reduced by making the magnetic path shorter.